Yarns, tows, and fibers having differential shrinkability

ABSTRACT

Differentially shrinkable tow of continuous filaments in which the filaments vary longitudinally thereof in latent shrinkage characteristic between predetermined minimum and maximum limits. The tow is converted into staple fiber lengths and spun into yarn.

United States Patent Ruddell et a1.

YARNS, TOWS, AND FIBERS HAVING DIFFERENTIAL SI-IRINKABILITY Inventors:James Nelson Ruddell, 19 Glenroy Ave., Portadown; Herbert AlexanderConway Todd, 25 Coolsara Park, Lisburn, both of Northern Ireland Filed:Feb

Appl. No.: 346,870

Related US. Application Data Continuation-impart of Ser. No. 219,048,Aug. 23,

1962, Pat. No.

3 ,302,3 85 Continuation-impart of Ser. No. 176,455, Feb. 12, 1962,abandoned.

Foreign Application Priority Data Aug. 26, 1961 Northern Ireland30850/61 Jan. 17, 1962 Northern Ireland 1796/62 Jan. 17, 1962 NorthernIreland 1797/62 May 25, 1962 Northern Ireland 20135/62 US. Cl. 57/140 R,28/72.17, 57/140 BY,

57/157 MS, 161/172 Int. CL... D02g 3/24 Field of Search 57/34, 55.5,157, 140;

28/1 C, 72 B, 72 F, 72.17; 161/170, 172,

[4 1 Dec. 10, 1974 Primary ExaminerJohn Petrakes Attorney, Agent, orFirm-William J. Daniel [5 7] ABSTRACT Differentially shrinkable tow ofcontinuous filaments in which the filaments vary longitudinally thereofin latent shrinkage characteristic between predetermined minimum andmaximum limits. The tow is converted into staple fiber lengths and spuninto yarn.

14 Claims, 17 Drawing Figures PATENYEBM: 10 m4 SHEET 8 OF 6 Arm flue uYARNS, TOWS, AND FIBERS HAVING DIFFERENTIAL SHRINKABILITY This inventionconcerns the modification of filaments forming or capable of formingassemblies of filaments such as tows, slivers, yarns and fabrics and isa continuation-in-part of our co-pending application Ser. No. 219,048filed 23rd Aug. 1962, now US. Pat. 3,302,385, itself acontinuation-in-part of our copending application Ser. No. 176,455 filed12th Feb. 1962, now abandoned.

The word filament is used herein, unless the context otherwiseindicates, to mean any element having a length which is many timesgreater than any of its crosssectional dimensions and in particulartextile filaments whether in the form of continuous filaments, staplefibres, or otherwise.

The broad object of the invention is to achieve new and improved effectsin assemblies of filaments.

A more particular object of the invention is to achieve new or improvedeffects in assemblies of textile filaments such as tows, slivers, yarnsand fabrics.

It is especially the object of the invention to produce from man-madefilaments yarns which resemble closely in many of their physicalcharacteristics, such as appearance and handle, and also in theirprocessing characteristics, yarns made from natural materials such aswool.

Further objects of the invention are to provide suitable processes andapparatus for carrying out the foregoing objects.

The manner in which these and other objects not specifically mentionedhereinbefore are achieved will now be described.

According to the present invention a continuous process ofsimultaneously treating a plurality of filaments adapted to form anassembly of filamentous material comprises the step of variablymodifying the ability of the filaments to shrink when subjected tofurther uniform treatment and so as to retain therein the modificationpending such further treatment. The invention also extends to theproducts of such a process and to machines and apparatus for puttingsame into practice.

More particularly the invention comprises a continuous method oftreating a tow of textile filaments which comprises the step of variablymodifying the ability of the filaments to shrink when subjected to afurther uniformly applied treatment and so as to retain therein themodification pending such further treatment, said modification varyingcyclically along the length of the filaments, the cycle length being notless than 60 inches and not more than 1,600 inches, and the maximumshrinkage differential being at least percent. The particular usefulnessof such a tow of filaments is manifested when converted into staplefibre, the mean staple length being such that 0z/2S is not less than 20and not more than 100 (a being the cycle length and S the mean staplelength), and the staple fibre into yarn, which is subsequently subjectedto said further uniformly applied treatment either before or afterfabrication. The yarn after treatment has many wool-likecharacteristics, For knitting yarn the maximum shrinkage differential ispreferably between percent and 25 percent (in the region of percentbeing particularly desirable for polyacrylics) and for weaving yarn andcarpet yarn, between 7.1/2 percent and 15 percent (in the region of 10percent being particularly desirable for polyacrylics).

The process is especially useful when the tow is of polyacrylicfilaments and there is considerable scope for variation of processingdetails within the scope indicated above, and'as will be apparent fromexamples set out hereinafter.

The invention also comprises a process in which the cycle length isequal to twice the staple length, the variability of the modificationbeing either continuous or discontinuous.

According to a further process within the scope of the invention aprocess of producing a continuous filament bulked yarn includes the stepof treating continuously and simultaneously as they are produced and inthe absence of twist a plurality of continuous filaments, having theability when heated to shrink substantially uniformly, variably tomodify said ability of the filaments to shrink so as to retain thereinthe modification pending a subsequent uniform heat treatment.

The invention will now be described more specifically with reference tothe accompanying drawings in which:

FIG. 1 is a diagrammatic representation of apparatus for converting acontinuous filament tow into yarn according to the invention;

FIG. 2 is a diagrammatic representation of another apparatus forconverting a continuous filament tow into yarn according to theinvention; 5

FIG. 3 is a diagrammatic representation of yet another apparatus forconverting a continuous filament tow into yarn according to theinvention;

FIG. 4 is a diagrammatic representation of apparatus for producingcontinuous filament yarn according to the invention, especially adjacentthe spinneret;

FIG. 5 is a diagrammatic representation of another form of apparatus forproducing continuous filament yarn according to the invention especiallyadjacent the spinneret;

FIG. 6 is a diagrammatic representation of apparatus for producingstaple fibre from continuous filament tow according to the invention;

FIG. 7 is a diagrammatic representation of apparatus for producingstaple fibre from continuous filament tow according to the invention;

FIG. 8 is a diagrammatic representation of a filament assembly accordingto the invention wherein a plurality of filaments are given alongitudinal variation in a characteristic thereof, for instanceshrinkage, the periodicity of the variation being the same for allfilaments in the assembly and the variation being in phase for allfilaments in the assembly;

FIG. 9 is a view similar to FIG. 8 except that the characteristic withineach filament is maintained constant, the variation thereof beingbetween filaments in the assembly;

FIG. 10 is another view similar to FIG. 8 except that the periodicity ofthe variation changes from filament to filament;

FIG. 11 is an additional view similar to FIG. 8 except that anintermediate filament has its characteristic altered in constantfashion, while that of the filaments on either side thereof isperiodically modified and in staggered relationship;

FIG. 12 is a view similar to FIG. 11, except that the periodicity of thevariation is considerably lengthened and the variations are less abrupt;

FIG. 13 is an enlarged cross-sectional diagram of a conventionalunbulked yarn from the prior art;

FIG. 14 is a view similar to FIG. 13 of a conventional high bulk yarn ofthe prior art;

FIG. 15 is a view similar to FIGS. 13 and 14 of a typical yarn formedaccording to the invention;

FIG. 16 is a diagrammatic elevation of the conventional high bulk yarnof FIG. 14; and

FIG. 17 is a view similar to FIG. 16 of a typical yarn producedaccording to the present invention.

In one method of processing a continuous filament tow of high shrinkagecharacteristics according to the invention the tow is passedcontinuously through a heated zone. Before entering the heated zone thetow is suitably tensioned, and means are provided to enable the tensionin the tow to be controlled within the heating zone and until it iscooled. For example, a set of feed rollers may be disposed prior to theheated zone and a set of takeup rollers after the cooling zone, thespeed of one or both sets of rollers being variable. In one suchembodiment the rollers are cylindrical and continuous cyclical changesin the speed of rotation of the takeup rollers relative to the feedrollers are employed to achieve a continuously varying shrinkage of thetow along its length. In another such embodiment conical rollers areused, and the position of the tow on the periphery thereof is. used tovary the shrinkage which takes place in the heated zone. When usingconical rollers and by causing the tow filaments to be dispersed overthe roller peripheries, varying shrinkage characteristics may beintroduced transversely of the tow instead of, or in addition to,longitudinal such variations. Clearly the nature and extent of thevariations can be controlled as desired within wide limits, and theywill be chosen so that'when the resultant continuous tow is cut intostaple, fibres will exist which have the desired different shrinkagecharacteristics. The conversion of the tow into yarn may take place inany suitable way, such as, for example on a Pacific or Rieter tow-to-topconverter, or by cutting into staple and carding in either case,followed by conventional drawing and spinning operations. It isimportant that the conversion should be carried out in away whichensures thorough mixing of the staple fibres and which does not destroythe differential shrinkage characteristics which have been given to thefibres. Finally the yarn is heat-treated at a suitably elevatedtemperature to cause the fibres to shrink differentially, whereupon theyarn structure is modified, owing to the interaction of the fibres asthe differential shrinkage takes place.

There appears in FIG. vl a diagrammatic illustration of one embodimentof apparatus for carrying out the method of this invention whichapparatus is particularly adapted for processing commercially availablepolyacrylic tow. According to this embodiment, the tow is passed fromany convenient source through two pairs of spaced-apart feed rollers 11and 12, respectively, arranged on either side of a steam chamber adaptedfor the passage of the tow therethrough. The roller pairs are driven bymeans of the respective motors l3, 14 which are adapted to have thespeed thereof altered over a considerable range by an appropriatecontrol. A fan 15 is provided between the outlet of the steam chamberand the second roller pair 12 to direct a cold blast of air against thetow. The purpose of the air blast from fan 15 is to impart to the towemerging from the steam chamber more rapid cooling than would exist inthe ambient atmosphere alone so that the tow has achieved a more stablecondition before encountering roller pair 12. After leaving roller pair12, the tow is advanced to machinery capable of converting the same intostaple fibres and ultimately into spun yarn. Such machinery is of typesconventionally employed in the art and may include, as appears in FIG.1, a staple cutting machine, a card, one or more draw frames, a rovingframe, and finally, a spinning frame. The staple cutting machine ispreferably of the type that can be adjusted to produce staple the lengthof which varies within narrow limits or is a chosen constant length.

The distance separating the roller pairs and hence the length of theheating zone as defined by the steam chamber and the cooling zone shouldpreferably be relatively small compared with the length of the tow overwhich a complete cycle of variations occurs. It is advantageous from thestandpoint of flexibility of operation for the steam chamber to bedesigned for operation under pressure or not, as desired, as well as forvarying the temperature of the steam supplied thereto. The followingexamples illustrate the operation of the apparatus of FIG. 1.

EXAMPLE 1 This example describes the processing of a 500,000 denier, 5denier per filament, commercially available polyacrylic tow made from aco-polymer which is 94 percent acrylonitrile and 6 percent vinyl acetate(Acrilan) on the apparatus of FIG. 1 to produce a woollike yarnaccording to the invention. The tow has initially a substantiallyuniform shrinkage characteristic of 20 percent, in saturated steam at212F.

The relaxing ratio of the roller pairs is caused to vary continuously byadjustment of one or both of roller driving motors from 1 to 0.82 whilstprocessing eighteen feet of tow, then from 0.82 to 1 Whilst processing afurther eighteen feet of tow and so on. The distance between the rollerpairs is much less than 18 feet, say about 3 feet. The temperature ofthe steam chamber is approximately 212F and the pressure atmospheric.The length of the steam chamber is approximately one foot and the linearspeed of the tow is 30 feet per minute. After emerging from the steamchamber and before passing between the rollers of pair 12 the tow iscaused to pass below the fan which blows a current of cold air over itto promote more rapid cooling to a temperature at which it is stable.From the roller pair 12 the tow is passed to the cutting machine bywhich it is converted to staple varying in length from 5 to 7 inches.The staple thus produced varies in its shrinkage characteristics insaturated steam at 212F over the whole range of 0 percent toapproximately 18 percent, and the distribution of the fibres withdifferent shrinkage characteristics is uniform over the range. Likewisethe distribution of fibres of different staple length is uniform overthe range of staple lengths. Within each staple fibre there will be acontinuous variation of shrinkage characteristic from end to end, butthis variation will be very small amounting to no more than a differenceof about /2 percent. The staple is then passed through a line ofconventional long staple flax type spinning machinery comprising card,draw frame, roving frame and spinning frame. The final yarn produced is24s worsted count, eight turns per inch.

The yarn is made into hanks and heat-treated in saturated steam at 2l2Ffor a period of minutes to develop its shrinkage Characteristics whichresults in a yarn which resembles in its essential physicalcharacteristics a woollen yarn. In handle and appearance it correspondsclosely to a woollen yarn. Its processing characteristics and inparticular its load-elongation and recovery characteristics alsocorrespond closely to those of a woollen yarn. The yarn is thereforesatisfactory for weaving and knitting into excellent fabrics, combiningmany of the more desirable qualities of both wool and polyacrylics, andwhich have, in particular, very good dimensional stability and creaseresistance.

EXAMPLE 2 In this case two ends of the singles yarn described in IExample 1 are plied before or after the final heattreatment described inthe previous example. In either case the result is a yarn which issatisfactory for weaving and knitting into excellent fabric, for examplemachine knitted outerwear of the fashion type for which wool andconventional high bulk yarns are presently used, and having the samequalities as the fabrics of example 1.

Some differences of appearance of the yarns may arise (reflected to alesser extent in the appearance of fabrics made therefrom), depending onwhether development of its varying shrinkage characteristics is carriedout before or after plying.

It will be clear that in a process involving treating the tow as in theforegoing examples the substantially uniform shrinkage properties of thetow as originally produced are modified in a variable manner so that bya subsequent treatment uniformly applied the staple fibre produced fromthe two may be caused to shrink differentially. It is thereforeimportant that the processing conditions employed should not be such aswould destroy the ability of the filaments to shrink. Thus whenprocessing a high shrinkage polyacrylic filament tow the use oftemperatures which are too high or processing times which are too longor both might render the differential shrinkage referred to impossibleand must therefore be avoided.

If heating of a polyacrylic filament tow is in the presence of moisture,the temperature should ordinarily be above 185F, whilst if carried outin dry air the temperature ordinarily should be above 260F. Preferablysaturated steam at approximately 212F is used. The time of passagethrough the zone should not be too short. When using such steamtreatment the time of passage through the treatment zone should not bemore than six seconds and it is preferred to reduce this time to onesecond if possible.

A wide variety of results may be obtained when processing filaments onapparatus such as that illustrated in FIG. 1 by adjusting certainvariables, the most important of which are the actual range of shrinkagecharacteristics induced in the filaments; the manner in which theshrinkage characteristics vary within that range; the length of thefilaments over which the shrinkage characteristics vary; and therelationship of the staple length of lengths of fibres cut from thefilaments to the foregoing. Further examples will now be given.

EXAMPLE 3 A tow similar to that of example 1 is processed on theapparatus of FIG. 1 in such manner that the distribution of the variableshrinkage characteristic throughout the mass of subsequently cut staplefibre is uniform. The staple length is arranged to be constant at sixinches, and there is negligible variation of the shrinkagecharacteristic within the individual fibres.

The staple fibre cut from the tow is processed on long staple flaxmachinery which gives thorough mixing and a yarn of 16s lea five turnsper inch is produced. From the yarn is produced a 4-ply three turns perinch yarn which is fully developed by heating to cause shrinkage in thesame way as the yarn in example 1.

The final yarn has an extension to break of 25 percent and a fibrepacking factor of 0.27. The instrument used for establishing theextension to break is the Uster single thread strength-testing machineand the instrument used for establishing the fibre packing factor is theBocking Geometer (described in the Journal of the Textile Institute Vol.50 No. 12 of December 1959 pages T.655 et seq. which is published inGreat Britain for the Textile Institute, 10 Black-friars Street,Manchester 3, England, by McCorquodale & Co. Ltd., Newton-le-Willows,Lancashire, England).

The yarn is very similar in appearance, handle and workability tocertain woollen yarns suitable for the hand knitting of outerwear. It isto be particularly noted that the load-extension and recoverycharacteristics of the yarn are very similar to those of woollen yarn ofcorresponding bulk and therefore the yarn is very suitable for hand ormachine knitting, unlike conventional high bulk yarn usually made frommixtures of two dis tinct types of staple, one with a given non-varyingshrinkage characteristic and one with a different nonvarying shrinkagecharacteristic. Such high bulk yarn has considerably less give" thanwoollen yarn and for this reason is not as easy to knit.

Fabrics knitted from the yarn of example 3 have all the desirableproperties associated with yarns made from fibres, such as polyacrylicfibres, which have low water imbibit-ion anda high natural ability torecover from deformation, and which therefore have what are usuallyreferred to as easy-care qualities, e.g. ease of laundering and dryingwithout the necessity of ironing. In addition the fabric is moreresilient than similar garments produced for examplefrom high bulk yarnand show great dimensional stability in washing. Furthermore the yarnwhen made up into fabric gives a welldefined clarity of stitch in theknitted fabric compared, for example, with similar fabric made fromconventional high bulk yarn made from similar fibres. Furthermore thefabric made from the yarn is more resistant to pilling and scuffing thanfabric made from conventional high bulk yarn.

EXAMPLE 4 Again a tow similar to that used in example 1 is processed onthe apparatus shown in FIG. 1. The variables are adjusted so that thedistribution of the variable shrinkage characteristic is not uniform.There is a substantially uniform distribution of fibres having from -5percent shrinkage but these form 20 percent of the total. There islikewise a substantially uniform distribution among the remaining fibreshaving shrinkage characteristics from -20 percent. It is also arrangedthat the fibre length varies from 5 to 7 inches and the distribution ofthe fibres of different staple lengths is uniform throughout the mass.Within each individual fibre there is negligible variation of shrinkagecharacteristic.

24s worsted eight turns per inch yarn is produced from the staple cutfrom the tow in the same manner as in example 3 which is then made 2-plyfive turns per inch and fully developed in the manner described inexample 1.

The final yarn has an extension to break of 25 percent and a fibrepacking factor of 0.24.

The yarn is much softer in handle than wool and in this respectresembles conventional high bulk yarn of similar fibre packing factor.Its load-extension and recovery characteristics, however, are similar tothose of a woollen yarn of corresponding bulk. Its other qualities aresimilar to those described in example 3 although there is a lesswell-defined clarity of stitch.

EXAMPLE 5 In this example a 500,000 denier, 5 denier per filament,commercially available polyacrylic tow made from a co-polymer which is94 percent acrylonitrile and 6 percent vinyl acetate is processed togive a woollike yarn. The tow has initially a substantially uniform zeroshrinkage characteristic in saturated steam at 212F.

The apparatus of FIG. 1 is used but in this case the variables areadjusted so that the tow is stretched differentially according to aprogramme as follows. The effective stretching ratio of the rollers iscaused to vary continuously from 1 to 1.12 when processing the firsteight feet of the tow; from from 1.12 to 1.3 when processing the nextfour feet of the tow; and from 1.3 to 1.4 when processing the next 8feet. This is a half cycle of the programme and the effective stretchingratio of the rollers in the next half cycle follows the reverse pattern.Thus the effective stretching ratio of the rollers varies from 1.4 to1.3 when processing the next 8 feet of tow, from 1.3 to 1.12 whenprocessing the'following 4 feet, and from 1.12 to 1 when processing thenext 8 feet. The full cycle is continuously repeated to give a tow 40percent of which has substantially uniform distribution of variableshrinkage characteristics within the range of 0 percent 10 percent,percent between 10 percent 20 percent and 40 percent between 20 percentpercent The tow is then cut to a staple length of six inches andprocessed on suitable long staple machinery to produce yarn of 24sworsted count with eight turns per inch Z twist. The yarn is two pliedwith 5 turns S twist and then fully developed as in example 1. Theresultant yarn is bulky with an open structure but more similar to ahigh bulk yarn than the yarn of the previous examples. It exhibits thesame advantages claimed in example 3 but to a lesser degree. i

If the effective stretching ratio on the third and fourth parts of thecycle are modified to vary from 1.3 to 1.5 then a range of 20 percentpercent instead of 20 percent 25 percent is given and slightly differentbut still useful yarn is produced.

EXAMPLE 6 In this example a carpet yarn is produced from a 15 denier perfilament high shrinkage polyacrylic tow.

The tow is processed on the apparatus shown in FIG. 1 with the variablesadjusted to give uniform distribution of variable shrinkagecharacteristic within the range 0-10 percent; a uniform staplelength ofsix inches; and substantially no variation of the shrinkagecharacteristic within individual fibres.

The staple fibre cut from the tow is crimped in a stuffing box and thenspun on the standard long staple machine carpet system to SS cottoncount three turns per inch and then folded 3-ply 1.1/2 turns per inch.

Shrinkage development is as described in example I.

The resultant yarn is of higher bulk than conventional carpet yarn madefrom synthetic fibres, but has a lower initial modulus which makes iteasier t0 process on the tufting machine. When tufted into carpet itexhibits high tread resilience and good covering power.

The foregoing examples it will be noted refer to the production ofpolyacrylic yarns for the reason that polyacrylic tow is currentlyreadily available in high shrinkage form and can very conveniently haveits shrinkage characteristic modified in accordance with the presentinvention by the method of differential relaxation employed in theforegoing examples. This particular mode of practising the invention is,however, as will readily be appreciated, applicable to any filamentwhich has a high shrinkage characteristic and which can have thischaracteristic modified differentially so as to be capable ofdevelopment by a subsequent treatment. Examples of other filaments arepolyamides, such as nylon, polyesters such as polyethyleneterephthalate, and polyolefins such as polypropylene.

The diagrammatic illustration of FIG. 2 is of a modified embodiment ofapparatus especially adapted for the processing of such other filaments.This modified embodiment is very similar to the embodiment illustratedin FIG. 1 except in two respects. First, the roller pairs 16, 17respectively, are driven at the same constant speed either by means ofconstant speed motors (not shown) or by appropriate control of motorssimilar to motors l3, 14 of FIG. 1. Second, the steam chamber isreplaced by a heating member 18 through which hot air is circulated soas to heat a tow passing in proximity thereto to a temperature which canbe varied cyclically over a considerable range.

The following example illustrates the practice of the invention on theapparatus of FIG. 2

EXAMPLE 7 In this example a polyethylene terephthalate tow of 200,000denier, 3 denier per filament, is processed in the apparatus of FIG. 2.The material is supplied by the producer so processed during and afterhot drawing step that it has a uniform shrinkage characteristic of 18percent when subjected to a temperature of 356F in the absence ofmoisture.

The heater 18 is so controlled as to heat the tow passing therethroughto a continuously varying temperature between the limits of 158F and356F. The temperature is caused to vary in a linear manner from maximumto minimum over eighteen feet of passing tow and back again over a likelength of passing tow. The tow so processed in an analogous manner tothe tow of example 1 is converted to 6 inch staple, and spun into yarn,which is then heat-treated at 3567F in the absence of moisture toproduce a yarn with a structure modified in a similar manner as inexample In this example it will be noted that a somewhat differentmethod is employed to modify the shrinkage characteristicdifferentially. The principal reason for this is that polyethyleneterephthalate has different processing characteristics to those of, say,polyacrylonitrile. Difficulties exist in processing polyethyleneterephthalate on the apparatus of FIG. 1 since in order to prevent thefilaments becoming set or partially set the processing speeds necessarywould give rise to practical problems. Of course setting or partialsetting would preclude or considerably diminish the subsequent shrinkagedevelopment which is necessary for the satisfactory practising of thepresent invention. The principles involved are in general the same,however, and the processing variables may be adjusted in an analogousmanner to the variables involved in the previous examples, and likewisedifferent end results may be obtained.

Where a viscose rayon tow is to be processed according to the invention,a further modification of the apparatus is preferably employed for thispurpose, as is illustrated diagrammatically in FIG. 3. As can be seen inthis figure, the tow is passed first through an aqueous bath 19containing a polymerizable resin-impregnating composition such as awater-soluble ethylene urea formaldehyde precondensate and a suitableresinifying catalyst, such as magnesium or ammonium chloride, and thenthrough a pair of driven nip rollers 20. The upper roller of the pair 20is supported for vertical movement and loaded resiliently by means of aspring 21, lever 22 and rotating arm 23. This system is so designed thatit operates to effect a variable expression of the bath liquid. Forexample it can be arranged to leave the ethylene urea formaldehyde resinon the tow in amount from 2 percent to 10 percent of the weight of thetow, the amount varying continuously from the maximum to the minimum andback again over successive 18 feet lengths of the tow. In practice toobtain such a range of expression a multiple bath system using baths ofdifferent concentrations might well be necessary but in the embodimentas illustrated, for simplicity, only one bath is shown.

The tow is then passed through a baking oven 24 maintained at asufficiently high substantially constant temperature, say within thelimits 302F to320F, to cure the ethylene urea formaldehyde condensate toan insoluble resin.

Next the resin treated tow passes through a bath 25 of warm water andthen through a bath 26 containing a solution of an appropriate fibrefinish (to aid spinning) dispersed in cold water (e.g. a 0.1 percentsolution of CIRRASOL HA, obtainable from Imperial Chemical IndustriesLimited). From this bath the tow passes through a hot air drier 27.After being dried the tow is processed on spinning machinery similar tothat already described with reference to FIG. 1, and finally the yarnthus produced immersed in aqueous caustic soda solution or likeshrinking agent. Thus, by using a caustic soda solution of 30 Twaddellplus 10 percent common salt the shrinkage varies from a maximum of about20 percent where the resin deposited is 2 percent to a minimum of 5percent where the resin deposited is 10 percent, so as to give rise to asimilarly modified structure to the yarn described in example 1. At someconvenient later stage it may be necessary to process the yarn or fabricmade therefrom so that all the fibres are cross linked or stabilized tosubstantially the same degree, for example by the application of acreaseresist resin. Otherwise, there may be a tendency during laterprocessing and use, particularly washing, for the specialcharacteristics of the yarn to be lost.

It is to be noted that although the process of this example depends onvariable expression of the resin treating bath liquid, the latter may bealternatively, or additionally (as stated), caused to vary in resinconcentration as the tow passes therethrough.

The foregoing examples all refer to the modification of the shrinkagecharacteristic of textile filaments and are examples of a very importantaspect of the present invention. These particular processes areapplicable to all filaments which can be put into a condition where theycan be shrunk differentially. In general all wholly syntheticthermoplastic filaments can be so treated along with many other manmadefilaments. Specific methods and apparatus have been described in theforegoing examples, but the particular method and apparatus chosen willdepend on the particular characteristics of the material from which thefilaments are made. Thus as has been shown in the foregoing examples itis preferred to process polyacrylic filaments in one particular manner,polyethylene terephthalate filamentsin another manner, and viscosefilaments in still another manner. Polyamide filaments can be processedaccording to the present invention in a similar manner to polyethyleneterephthalate filaments. Generally speaking polyamide filaments arecurrently available, however, with a total shrinkage characteristic ofabout 10 percent which would limit the range of end results obtainable.However, polyamide filaments with a higher total shrinkagecharacteristic can be produced thus enabling the range of end results tobe extended. Furthermore polyamide filaments can be given variableshrinkage characteristics by chemical processing in which a chemical,causing fibre shrinkage, is applied differentially to the filaments,subsequent development being by uniform application of the chemical tothe filaments. An example of such a chemical is phenol in aqueoussolution ofa concentration less than 4.1/2 percent. Furthermore althoughthe foregoing examples relate to high shrinkage tows similar principlesare applicable to fully relaxed tows in which case differentialshrinkage could be induced by differential stretching, and without itbeing necessary to use heat, although heating can be employed ifdesired.

The foregoing examples are also all directed to the production of yarnsfrom staple fibre in accordance with the present invention and furtherexamples will now be given also relating to production of yarn fromstaple fibre, but illustrating that it is not necessary for i all thestaple fibre which is used to have been produced according to thepresent invention, or if so produced to be of the same type.

EXAMPLE 8 In this example 5 denier per filament high shrinkagepolyacrylic tow is processed on the apparatus of FIG. 1. Thedistribution of the variable fibre shrinkage characteristic is uniformand the range from 0-10 percent. The staple length is uniform at 6inches and there is substantially no variation of shrinkagecharacteristic within individual fibres. The staple fibre cut from thetow is carded and the slivers produced are blended O 50 with slivers of56s quality wool combed top on the conventional worsted system and spunto s worsted count yarn. The yarn exhibits fairly even distribution ofthe different fibres with perhaps a tendency for the wool to predominateat the outside.

The final yarn has an extension to break of 22 percent and a handlesimilar to that of yarn made from wool. The yarn is not subject toshrinkage or other conditions to develop its varying shrinkagecharacteristics but woven into fabric having ends per inch and 35 picksper inch. This fabric is developed by immersing in water atapproximately 2 l 2F in a tensionless condition. Care is exercised notto allow the fabric to crease before it is cooled. The fabric thusdeveloped has approximately 39 ends per inch and approximately 39 picksper inch. It has a warp and weft crease recovery value of 150 by theBritish Standard Method of Tests for the Recovery of Fabrics fromCreasing, BS 3086; 1959, published by British Standards Institute,British Standards House, 2 Park Street, London W.l, and

printed by Baynard Press, London S.W.9. The fabric is very similar to acorresponding woollen fabric, has easy-care qualities and is suitablefor skirts and suitings. It is particularly stable dimensionally.

EXAMPLE 9 g the apparatus from the 6 denier per filament tow had auniform distribution of fibre shrinkage characteristic within the rangeof 10-18 percent and a uniform staple length of 6 inches. In both casesthere was a negligible variation ofthe shrinkage characteristic withinthe individual fibres. The two component staple fibres were blendedtogether in the proportions 60 percent (0-10 percent shrinkage fibre)percent (l0l8 percent shrinkage fibre) and the resultant blend spun onthe flax system to s lea ten turns per inch singles. This was then usedto produce 2-ply six turns per inch yarn.

The final yarn was developed in the same manner as in example 1 andwoven into a plain ,fabric with 25 picksper inch and 25 ends per inch.

The yarn after development had an extension to break of 26 percent and ahandle similar to that of yarn made from wool. The yarn was of openstructure throughout, the inner portion consisting predominantly of the6 denier fibres and the remainder consisting predominantly of 3 denierfibres. The fabric had a crease recovery value of 156 (weft) and 154(warp) by the Monsanto or Shirley test. A soft handle was also evident.

There are several known methods of producing continuous multifilamentbulked yarns, for example, those methods based on false-twisting thefilaments, passing the filaments over a heated sharp edge, subjectingthe filaments to an air blast, and passing the filaments through astuffer-box. All such methods, however, involve additional processing ofthe yarn as supplied by the producer that is to say, by throwingoperations.

In the embodiments of apparatus thus far described, all of the strandsin the given tow assembly are processed in like manner, the variationscreated therein varying uniformly across the entire assembly. It iswithin the scope of the present invention, however, to producevariations which differ or are non-uniform in corresponding regions ofthe filaments making up the assembly. One embodiment of apparatus forproducing this effect is illustrated diagrammatically in FIG. 4 of theaccompanying drawings. Such apparatus is disposed so that a plurality ofcontinuous filaments as pro duced in the known manner from a spinneretand its associated drawing system can be passed continuously in theabsence of twist therethrough. Of course the method could be applied asan additional process at some later time if desired.

In the apparatus of FIG. 4 a continuous sheet 30 of synthetic filamentshaving a relatively low uniform shrinkage characteristic say, of lessthan 10 percent for polyacrylic filaments, and thus capable of beingfurther drawn to a substantial degree are passed side-by-side through adrawing system which includes two spaced pairs 28, 29 of conicalrollers. Both the rollers of the first pair 28 have their smaller endsin juxtaposition at one edge of the sheet of filaments 30, whilst boththe rollers of the second pair 29 have their smaller ends at the otheredge of the sheet of filaments 30. Both pairs of rollers 28, 29 aredriven at like peripheral speeds and are linked by a mechanism 31 whichrepeatedly causes the rollers of each pair 28, 29 to separate in turn.Thus, the filaments will be successively and repeatedly under thedrawing influence of first one pair of rollers 28 and then the otherpair 29. When under the influence of the one pair 28, the filament atthe smaller ends of the rollers will be stretched a minimum amountwhilst the filament at the larger ends of the rollers will be stretcheda maximum amount. The filaments inbetween will be stretched to varyingdegrees between the two extremes. When under the influence of the otherpair the effect will be reversed, since the filament previouslysubjected to minimum stretch will now be subjected to maximum stretchand vice versa. The roller pairs are similarly dimensioned and the sheetof filaments extends over like parts thereof, and so the filaments at ornear the centre of the sheet will always be stretched by substantiallythe same amount. It will usually be necessary to provide a compensatingsystem 32 associated with the roller pairs 28, 29 because the filamentswill, from time to time, have different linear speeds. The system 32will include a movable roller, under which the filaments pass, which isadjusted in position continuously to deflect the filaments in such amanner that a substantially constant tension is preserved in each.

After passing through the drawing system all, or nearly all, thefilaments will have been stretched by varying amounts along theirlength, depending on the speed of the conical rollers and the frequencyof the change over from one pair to the other, the effect being variablealso across the sheet of filaments.

The filaments are subsequently twisted to form a yarn and then shrunk byuniform heat-treatment. Since the amount of shrinkage at any given partof a filament at a given temperature depends on the amount that part ofthe filament has previously been stretched, the shrinkage will differalong the length of each filament and also transversely of the yarn, theresult beingthat, in any short length of the yarn the filaments whichshrink least are caused by the other filaments to loop and spread, whichgives the yarn as a whole increased bulk without high stretch at lowloads. The effect may, if desired, be further varied by changing thetwist in the yarn.

The general technique utilized in connection with the apparatus of FIG.4 can be readily adapted to the needs of filaments which by their natureexhibit a better response to a heat treatment than to a stretchingoperation, such as those formed of polyethylene terephthalate polymer,by substituting for the variable stretching means of FIG. 4, a means forapplying to the filaments a variable heat treatment. Thus, as shown inFIG. 5, the filaments in this case are processed in a manner analogousto that used in the embodiment of FIG. 4 except that instead of conicalrollers, two hot air heaters 33, 34 are used through which the filamentsare passed at a constant speed by feed and withdrawal roller systems(not shown). Their heating effect is arranged to vary across the sheetof filaments. The first heater 33 when in operation causes the filamentsat one edge of the sheet to be heated to a relatively high temperatureat which the filaments exhibit maximum shrinkage and the filaments atthe other end of the sheet to relatively low temperature at which noshrinkage occurs with a selected temperature gradient therebetween. Theother heater is arranged to have a reverse effect. As in the case of therollers of the previous example the heaters are brought alternately intooperation. The result of this is that the filaments are given markedlydifferential shrinkage characteristics in like manner to that appearingin filaments processed in the apparatus of FIG. 4. The following exampleillustrates the operation of the embodiment of FIG. 5.

EXAMPLE Filaments of polyethylene terephthalate which are produced witha uniform shrinkage characteristic of percent at 356F in the absence ofmoisture are processed in the absence of twist in the apparatus of FIG.5, the heating action of the first heater 33 being such as to heat thefilaments at one edge of the sheet to a temperature of 356F and thefilaments at the other end of the sheet to a temperature of 122F, withthe filaments between the two edges varying uniformly between theseextremes. The temperature gradient of the second heater 34 is made to beprecisely opposite from that of the first heater 33. The heatertemperature and yarn rateof travel therethrough are regulated in suchamanner that a variable shrinkage characteristic of from 0 percent to 18percent is induced. When twisted and subjected to a suitable furtherconstant temperature heat treatment the yarn bulks as the differentialshrinkage takes place. i

In another procedure for producing a bulked continuous filament yarn acontinuous sheet of polyacrylic filaments having a shrinkagecharacteristic of less than 2 percent are passed over a hot godet heatedto 280F and then to a cold godet held at 50F. The godets are linked by avariable speed drive, the hot godet being driven at a suitably constantspeed while the cold godet is varied in speed in a cyclic manner overthe range 1.01-1.25 times the speed of the hot godet. The sheet offilaments delivered by the cold godet is passed over a spreader rollerand a series of fixed guides which are so positioned to ensure that thepassed length traversed by the various filaments across the width of thesheet from the spreader roller to a delivery roller varies between P andP +a/2 where P is the shortest distance between the spreader roller andthe delivery roller and a is the filament length passing during onecycle of speed variation of the cold godet.

By reason of the variable drawing introduced between the two godets thesheet of filaments emerging from the spreader roller has in it a cyclicvariation in shrinkage characteristics of the order of 0-20 percent.This variation exists in each filament and is in phase from filament tofilament. The guides cause the filaments to be displaced longitudinallyat the delivery roller so that the variation becomes out of phase to themaximum extent possible between the filaments, the phase change varyingfrom 0 to 01/2 across the sheet. Thus the filament assembly has beenconstructed such that in any cross section thereof each filament willhave a different shrinkage characteristic varying from 0 percent 20percent approximately. When the assembly thereafter has twist insertedinto it and is exposed to steam at 212F the parts of the filaments withthe higher shrinkage characteristics will tend to buckle those with thelower shrinkage characteristics and so form an open structured bulkedfilament yarn which will have desirable tensile characteristics orproperties in that its extension under low loads will be similar to thatof bulked spun yarns of the type previously described. Such yarns willresult in more stable fabrics demanding less critical processingconditions in winding, weaving and knitting operations.

If desired, the treatment effective to impart to the filaments thevariable shrinkage characteristics can be carried out in conjunctionwith the staple cutting step of the over-all process instead of in aseparate prelimi nary step as has been the case in the embodiments thusfar described. One form of apparatus in which the variable shrinkagetreatment and the staple cutting steps are carried out concurrently isillustrated in FIG. 6. As shown in this Figure the tow is fed by meansof a pair of nip rollers 35, 36 rotating at constant speed to anotherpair of rollers of special design whereby the tow is reduced to staple.The lower roller 37 of the second pair is of rubber and is cylindricaland concentrically mounted. The upper driven roller 38 which is surfacedwith rubber carries cutters 39 at spaced intervals around its peripheryand is eccentrically mounted, its bearings being arranged to reciprocatealong the line of centres of the two rollers. Means 40 for directing asteam jet on the tow as it enters the nip between the rollers of thesecond pair is provided. It is important that the filaments are cooledbefore they emerge from the nip of the second pair of rollers and thepoint of application of the steam jet is chosen accordingly and specialcooling means, such as means 41 for projecting a jet of cooling air onroller 38, provided if necessary. The speed of rotation of the secondpair of rollers, the spacing and position of the cutters and theeccentricity of the top roller areso chosen that staple of appropriatelength is cut from the tow, each fibre, due to the continuously varyingperipheral speed of the top roller, resulting from its eccentricity,having been relaxed in a continuous variable manner, say, from percentto 20 percent from end to end.

EXAMPLE l2 Yarn is spun from the staple prepared by processing a highshrinkage tow of polyacrylic filaments on the apparatus of FIG. 6 at therelaxation range of 6-20 per cent and when appropriately heat-treatedexhibits a structure which varies from very open at the outside to quitecompact at the core.

Clearly the nature of the variation in the fibres may be controlled inmany different ways and different end results thereby obtained.

Concurrent reduction of the tow into staple and introduction of thevariable shrinkage characteristic to the filaments thereof can also beaccomplished with a different type of known staple cutting machine,according to which a cutting blade is passed transversely across amoving sheet of filaments. One such apparatus embodying the presentconcept is diagrammatically illustrated in FIG. 7. According to theapparatus of FIG. 7, a suitable high shrinkage tow, for example ofpolyacrylic filaments, is cut into staple by a cutter 42 of the Nordholmor Braidwater type carrying a steam nozzle 43 at a given distance behindthe cutter blade. The details of the mounting and operation of thecutter 42 and associated steam nozzle 43 have not been shown since theyare either well-known in the art or obvious to a person skilled in theart. In this way a part of each fibre is automatically steam relaxed soas almost completely to inihibit any further heat shrinkage thereof. Inthis case the variation of the shrinkage characteristic is substantiallydiscontinuous, and when the staple is spun into yarn, and the yarnsubsequently subjected to an appropriate heat-treatment the latterexhibits a more sharply defined transition from a compact core to anopen-structured surface,

Discontinuous variations in the shrinkage characteristics of a group ofcontinuous filaments may be obtained by similar means but withoutcutting.

When producing staple fibres according to the invention the effect ofsubsequent processing steps should be taken into consideration. Forexample, it is often desirable, if producing sliver using a card otherthan a flax card, to have crimp in the fibres. The step of imparting thecrimp after the fibres have been subjected to variable modification,may, and often does, cause the temperature of the fibres to be elevated,and such elevated temperatures will in certain cases modify the variablecharacteristics produced by the processing according to the invention.This will be so, for example, where the characteristic is shrinkage onsubsequent heat- 7 treatment if the temperature reached in crimping issufficiently high. It is, however, fortunately, a simple matter tocompensate for this by introducing a correspondingly greater variabilityin the first place, so that the desired end result is still achieved.The alternative would be to choose a crimping method where a rise intemperature does not occur, or is so small as not substantially toeffect the variability of the characteristic.

It will be appreciated that several of the foregoing examples whichspecify that the development takes place for instance in the yarn beforeit is fabricated could be modified so that development takes place afterfabrication. Clearly the selected time of development will depend on theparticular type of desired end result. Thus if development takes placein the fabric the yarn modification will, to some extent, be restrictedby the inter relation of the fabricated ends of yarn. Of course, if theyarn is to be dyed before fabrication, it almost inevitably follows thatdevelopment will have to take place at the time of dyeing.

As has been stated the foregoing examples all relate to the treatment oftextile filaments and involve the modification of the shrinkagecharacteristics thereof. It will be clear that the possibilities ofvariation on this theme are numerous and the same would apply where theproperty was some property other than the shrinkage characteristic. Inorder to illustrate these possibilities it will be convenient to analysefully the application of the invention by way of example to textilefilaments and utilising the ability of certain such filaments to havetheir shrinkage characteristic modified in a variable manner. Thus,according to the present invention, the following may be produced:

I. A group of continuous filaments each filament having a like varyinglongitudinal shrinkage characteristic. This is achieved for example byproviding pairs of cylindrical rollers before and after a heated Zone,between which tow passes, and continuously varying their relative speed,as in example 1, before cutting takes place.

FIG. 8 illustrates such a group of continuous filaments and thevariation of the shrinkage characteristic is shown in this Figure by thethickness of the line representing each individual filament. It is to bestressed that this is merely a convention and is not intended toindicate the specific variation in the cross-sectional dimension of thefilament.

It is also pointed out that in this Figure and in FIGS. 9 to 12 suchfilaments have been shown for the purposes of illustration and notlimitation. In practice there would of course usually be a far greaternumber than this.

When the material of this group is in the form of a tow it will normallybe used for producing staple fibre and in this connection referenceshould be made to group IV hereunder.

When the material of group I is in the form of a continuous filamentyarn it can be utilized in accordance with the present invention in anumber of different ways. For example it could be combined with anatural yarn and then a subsequent development treatment employed toproduce, say, a fancy yarn.

It may be used in a fabric either alone or with other yarns. Thus forexample if woven alone in a suitable pattern into a fabric and thendeveloped a seersucker effect would be obtained. Yet another way ofutilising such a yarn would be to cause the filaments to be displacedlongitudinally relative to one another say by twist or air blast or bycausing them to traverse a varying path length, before developmentwhereafter a bulking effect is achieved.

II. A group of continuous filaments each (or many) having a differentbut unvarying longitudinal shrinkage characteristic. This may be, forinstance, achieved by producing a pair of cylindrical nip rollers beforea heated zone, and a pair of conical nip rollers after the heated zone,the speeds of the two pairs being fixed and passing tow through thesystem.

FIG. 9 illustrates filaments of this group the differential shrinkagecharacteristic being illustrated by use of the same convention adoptedin FIG. 8.

In the form of tows filaments of this group may be reduced according tothe present invention to staple fibre (see group IV hereunder).

In the form of continuous filament yarn interesting possibilities exist.It is difficult to envisage a commercial method of producing such yarnwhich will not involve an output in which the length of the individualfilaments produced per unit time does not vary. One method ofcompensating for such a variable output would be to twist the yarnappropriately whereby to produce a yarn with successive compact nodeswith a more open structure between the nodes. Although on developingsuch a yarn the bulk would be reduced, such yarns are useful inproducing a woven fabric of very even structure. In this case the fabricwould be woven from the. yarn before development and the developmenttreatment applied to the finished fabric. In this way the initial bulkof the yarn would govern the spacing of the ends and picks and when thebulk was reduced or removed by the development treatment a fabric ofvery even structure would result.

III. A group of continuous filaments each (or many) having a differentand varying longitudinal shrinkage characteristic. This is achieved, forexample, by providing a pair of cylindrical rollers before the heatedzone and a pair of conical rollers after the heated zone and varyingtheir relative speed.

FIG. illustrates such a group of filaments using the same convention asbefore.

Continuous filament tows, like those of the previous groups, could beused to produce staple fibre from which yarns would be spun and in thisconnection reference should be made to group IV hereunder.

In the form of continuous filament yarn there are a widerange ofpossibilities and the continuous filament yarns of groups I and II mightbe considered as being special limiting cases in this range. It is to benoted that there is again the problem, as with continuous filament yarnsof group I], of the variable output. In order to avoid the problem ofvariable output the filaments may be processed, for example, in themanner illustrated in FIG. 4, and FIG. 11 illustrates the manner inwhich the shrinkage characteristic varies in the group of filaments totreated. The discontinuities longitudinally of each filament will benoted but there is of course a continuous variation of shrinkagecharacteristic transversely of the yarn. Furthermore, thediscontinuities would be displaced by twist and no unevenness along thelength ofthe yarn would occur on development. FIG. 12 illustrates agroup of filaments produced as illustrated in FIG. 5. In this case thelongitudinal discontinuities are not so pronounced.

IV. A group of staple fibres including a number of types havingdifferent shrinkage characteristics. This may be achieved by convertingany one or more of the groups of continuous filaments of I, II and IIIabove into staple. The number of different types depends on the group orgroups used and the number of filaments in it. The variation ofshrinkage characteristics along the length of each fibre may be arrangedto be substantially none up to a high variation according to therelationship between staple length and the processing conditions chosen.

Many of the specific examples given heretofore illustrate such groups ofstaple fibres and their usefulness.

V. A group of staple fibres each fibre having like variable longitudinalshrinkage characteristics. This may be achieved by producing a group ofcontinuous filaments of group I, and suitably synchronising the cuttingof the staple with the variable processing conditions, by using aneccentric cutter as in the embodiment of FIG. 6 (the variation beingcontinuous) or by using a Nordholm or Braidwater cutter in the mannerdescribed in the embodiment of FIG. 7 (the variation being substantiallydiscontinuous).

As has been indicated yarn produced from group IV staple fibres are ofconsiderable interest and importance and when describing yarns producedfrom such staple fibres in the foregoing examples reference has beenmade for comparison purposes to conventional high bulk yarn producedfrom synthetic staple fibre. In order to aid a fuller understanding ofthe invention the structure of various yarns both conventional andaccording to the present invention will now be described.

FIG. 13 is intended to illustrate a cross section taken through aconventional unbulked yarn made from synthetic staple fibre all of agiven shrinkage characteristic.

FIG. 14 illustrates to substantially the same scale a cross sectionthrough a conventional high bulk yarn made from synthetic staple fibreof two different shrinkage characteristics. The dark circles representfibres with the higher shrinkage characteristic and the light circlesthe fibres with the lower shrinkage characteristic. The preponderance offibres with the higher shrinkage characteristic at the core of the yarnis due to the tendency of these fibres to loop in and out of the coreover relatively long distances, that is to say a substantial length ofeach fibre tends to remain in the core. The fibres having the lowershrinkage characteristic, on the other hand, tend toloop in and out ofthe core rapidly so that a relatively short portion thereof remains inthe core.

FIG. 16 is a diagrammatic elevation to a large scale of a yarn of thistype, but for clarity the number of fibres at any cross-section is tencompared with forty in FIG. 14. Furthermore, no fibre ends are shown inthe short element illustrated.

FIG. 15 is a cross section through a yarn spun from synthetic staplefibres produced according to the invention the fibres havingsubstantially a continuum of different shrinkage characteristics. Inthis case the different shrinkage characteristics are illustrated bydifferent letters of the alphabet. The yarn of example 1 would be a yarnof this type, and it is assumed that there is negligible variation ofshrinkage characteristic longitudinally of each fibre.

FIG. 17 is a diagrammatic elevation to a large scale ofa yarn of thistype, but, again, for clarity the number of fibres at any cross sectionis only ten, and no fibre ends are shown.

A yarn which may loosely be described as somewhere between aconventional high bulk yarn and the yarn illustrated in FIG. 15 may beproduced by utilising staple fibre falling within group V and having acontinuous variation along each fibre. The tendency of such a yarn willbe to have a greater compactness at the core than that illustrated inFIG. 15. This tendency may be exaggerated by utilising staple fibre ofgroup V with discontinuous rather than continuous variation in theshrinkage characteristic and whilst in appearance, handle and tensileproperties such a yarn would be very similar to a conventional high bulkyarn, it differs from such yarn in that instead of looping in and out ofthe core there is a tendency for all the fibres to become anchored atone end in the core and usually with the other end at or near thesurface of the yarn. Such a yarn is particularly useful for themanufacture of blankets and other types of brushed fabrics since thebrushing is facilitated and there is less shedding of fibres.

Although the majority of the foregoing examples have been concerned withthe production of what may be described as bulked yarns from whollysynthetic thermoplastic filamentous material, and involve the step ofcausing such material to have variable shrinkage characteristics, it isto be understood that the invention is by no means limited to suchprocedure. Thus, textile filaments may be treated in accordance with theinvention so that they are given a differential affinity for a dyestuff.One method of achieving this would be to treat the filament surface witha suitable resin in a variable manner whereupon on subsequently havingapplied thereto a suitable uniform dyeing process a correspondingvariable uptake of dye will occur, the resin being removed during orafter dyeing if necessary or desirable. One of the main applications ofsuch embodiments is to enable man-made filaments to dye in a similarmanner to natural fibres. For example wool fibres have differentialdyeing properties whereas manmade fibres tend to have much more uniformsuch properties. As a consequence tartans, for instance of man-madematerials, never seem to have the appearance of woollen tartans, andthis is thought to be a result of the aforesaid difference. Furthermore,differential crease-resistant properties could be given to fibres by thedifferential application of crease-resist finishes thereto in accordancewith the invention. Also, the invention is not limited to the treatmentof wholly synthetic thermoplastic yarn (as evidence by the foregoingexample relating to viscose rayon) or even to other man-made fibres orfilaments. Thus, a sliver of flax could have applied to it in irregularfashion a protective treatment which would result in the fibres havingdifferential shrinkage characteristics capable of manifesting themselvesafter spinning under the influence of a suitable further treatment.

Furthermore, it is clear from the examples that a variety of simplemeans exist for endowing the particular material being treated with thedesired variable latent characteristics, and for this reason the variousmechanical and other means have been illustrated in diagrammatic formonly. It is also clear that the group of filaments or fibres treatedaccording to the invention may be quite small or very large. Thus, forexample, a number of tows may be treated simultaneously in similarmanner as in examples 1 to 4 and supplied to a can before furtherprocessing. Furthermore, if, as has already been stated, instead of ahigh shrinkage tow, as described for instance in example 1, a relaxedtow is treated, the same principles are involved except that in order togive it variable shrinkage characteristics variable stretching ratherthan variable relaxation takes place in the heated zone.

We claim:

1. A tow of continuous filamentary textile material adapted tobe'subdivided into staple fibers of generally predetermined length inwhich the continuous filaments thereof cyclically vary in gradual andcontinuous manner in latent shrinkage characteristic longitudinallythereof between predetermined minimum and maximum limits ofsignificantly different values, the length of the cycle of saidvariation being substantially greater than said predetermined length ofsaid staple fibers.

2. Staple cut from the tow of claim 1.

3. Spun yarn produced from the staple of claim 2.

4. The tow of claim 1 wherein said cyclical variation in latentshrinkage characteristic occurs uniformily in at least substantially allof the filaments in said tow.

5. The tow of claim 1 wherein the length of said cycle ranges from aboutinches to about 1,600 inches, and the difference between said maximumand minimum values is at least 5 percent.

6. Staple fiber produced from the tow of claim 5 wherein the mean staplelength is selected to give a ratio relative to the cycle length withinthe range of 1/40 1/200.

7. The tow of claim 5 wherein the maximum latent shrinkage value differsfrom the minimum value by about 25-30 percent.

8. Staple fiber produced from the tow of claim 7 and having adistribution of fibers therein such that 40 percent have a latentshrinkage varying from the minimum value to the minimum value plus l0percent, 20 percent have a latent shrinkage varying from the minimumvalue plus 10 percent to the minimum value plus 20 percent, and 40percent have a latent shrinkage varying from the minimum value plus 20percent to the maximum value.

9. The tow of claim 1 wherein said cycle length is at least twice thegenerally predetermined length of said staple fibers.

10. A tow of continuous man-made textile filaments in which thecontinuous filaments thereof vary in latent shrinkage characteristicgradually and continuously from filament to filament across the tow froma minimum value to a significantly different maximum value, thecharacteristic of each of substantially all of said filaments being atleast slightly different from that of the other filaments, the latentshrinkage characteristic of each filament also varying longitudinallythereof between minimum value and a significantly different maximumvalue.

11. Staple cut from the tow of claim l0.

l2. Spun yarn produced from the staple of claim 11.

13. The tow of claim 10 wherein said longitudinal variation occurscyclically along the length of the filaments, the length of said cycleranging from about 60 inches to about 1,600 inches and differencebetween each of said minimum and maximum values is at least 5 percent.

14. Staple fiber produced from the tow of claim 13 wherein the meanstaple length is selected to give a ratio relative to the cycle lengthwithin the range of H40 -l/200.

1. A tow of continuous filamentary textile material adapted to besubdivided into staple fibers of generally predetermined length in whichthe continuous filaments thereof cyclically vary in gradual andcontinuous manner in latent shrinkage characteristic longitudinallythereof between predetermined minimum and maximum limits ofsignificantly different values, the length of the cycle of saidvariation being substantially greater than said predetermined length ofsaid staple fibers.
 2. Staple cut from the tow of claim
 1. 3. Spun yarnproduced from the staple of claim
 2. 4. The tow of claim 1 wherein saidcyclical variation in latent shrinkage characteristic occurs uniformilyin at least substantially all of the filaments in said tow.
 5. The towof claim 1 wherein the length of said cycle ranges from about 60 inchesto about 1,600 inches, and the difference between said maximum andminimum values is at least 5 percent.
 6. Staple fiber produced from thetow of claim 5 wherein the mean staple length is selected to give aratio relative to the cycle length within the range of 1/40 - 1/200. 7.The tow of claim 5 wherein the maximum latent shrinkage value differsfrom the minimum value by about 25-30 percent.
 8. Staple fiber producedfrom the tow of claim 7 and having a distribution of fibers therein suchthat 40 percent have a latent shrinkage varying from the minimum valueto the minimum value plus 10 percent, 20 percent have a latent shrinkagevarying from the minimum value plus 10 percent to the minimum value plus20 percent, and 40 percent have a latent shrinkage varying from theminimum value plus 20 percent to the maximum value.
 9. The tow of claim1 wherein said cycle length is at least twice the generallypredetermined length of said staple fibers.
 10. A tow of continuousman-made textile filaments in which the continuous filaments thereofvary in latent shrinkage characteristic gradually and continuously fromfilament to filament across the tow from a minimum value to asignificantly different maximum value, the characteristic of each ofsubstantially all of said filaments being at least slightly differentfrom that of the other filaments, the latent shrinkage characteristic ofeach filament also varying longitudinally thereof between minimum valueand a significantly different maximum value.
 11. Staple cut from the towof claim
 10. 12. Spun yarn produced from the staple of claim
 11. 13. Thetow of claim 10 wherein said longitudinal variation occurs cyclicallyalong the length of the filaments, the length of said cycle ranging fromabout 60 inches to about 1,600 inches and difference between each ofsaid minimum and maximum values is at least 5 percent.
 14. Staple fiberproduced from the tow of claim 13 wherein the mean staple length isselected to give a ratio relative to the cycle length within the rangeof 1/40 -1/200.